Biology of Amphibians
Last Review/Updated: May 30, 2002
Amphibians form a distinct class of vertebrates with over 4000 species world-wide. Within this class, there are four orders. Only two, the Caudata (the salamanders) and the Anura (the frogs and toads), are found in Canada.
Amphibians have no unique anatomical structure, such as the feathers of birds, which sets them apart from all other animals. However, there are some characteristics that all amphibians share:
- they are ectothermic (sometimes referred to as cold-blooded); their body temperature varies with that of the environment.
- they have soft, generally moist skin without scales.
- they lay eggs without shells and so to prevent the egg from drying up they must be laid either in water or a damp environment.
Of course the most obvious characteristic of amphibians is their two-stage life history. When amphibians hatch from their eggs they are in a gilled larval form. In frogs and toads, these larvae are referred to as tadpoles. After several weeks or months, these larvae metamorphose into the adult air-breathing shape. Some individuals remain in the aquatic stage and continue to grow and mature. This phenomenon (referred to as neoteny) is common in the tiger salamander.
Introduction | Identifying
Amphibians | Biology of Amphibians | Global
Decline
Amphibian Monitoring Project | RANA
Project
